The present invention relates to a process for producing a high-purity maltose.
Recently, various advantages of maltose in food products and pharmaceuticals have been established one after another. Thus its uses have expanded rapidly. These expanded uses have inevitably led to increasing demands for a high-purity maltose.
Conventionally, maltose has been available as a saccharified starch product with a maltose content of about 40-50 w/w% based upon the weight of the dry solid solute (all percentages as used in the specification mean "weight percentages on dry solid basis" unless otherwise specified) which is obtainable by subjecting a liquefied starch solution to the action of a malt enzyme.
Recent advances in starch saccharification techniques have somewhat simplified the production of a saccharified starch product with a maltose content of 50% or higher, for example, by the combined treatment of starch with .beta.-amylase and starch debranching enzyme.
The above described starch saccharification technique, however, from economical and technical standpoints, renders the direct production of a high-purity maltose with a maltose content of 90% or higher very difficult.
Some processes for obtaining a high-purity maltose are disclosed in recent patent applications. In some of these processes, a starch sugar solution containing maltose is passed through a column of an anion exchange resin. For example, Japanese Patent Publication No. 46,290/77 discloses a process for producing a high-purity maltose comprising preparing a starch sugar solution substantially consisting of dextrin and about 65% maltose, and applying the solution to an anion exchange resin of OH-form to adsorb the maltose constituent and also to remove the dextrin constituent. Since, however, in such a process the maltose constituent is adsorbed on the anion exchange resin of OH-form, the solution should be applied to the resin at the lowest possible temperature, preferably, below 20.degree. C., to prevent the isomerization of the maltose constituent. Thus, increased viscosity and microbial contamination as well as low purification capability result, rendering its industrial-scale practice very difficult. Further, Japanese Patent Publication No. 20,579/79 discloses a process for producing a high-purity maltose which comprises applying a starch sugar solution, containing glucose and maltose, to a column packed with an anion exchange resin of SO.sub.3.sup.2- - or SO.sub.3 H.sup.- -form, to fractionate the solution into the glucose- and maltose-constituents. The process is, however, inadequate as a process for industrial-scale production of a high-purity maltose because the bonding of the SO.sub.3.sup.2- - or SO.sub.3 H.sup.- -group is labile.